Abstract
Visible light photocatalysis is a tool in synthetic chemistry that allows us to utilize the energy of photons via photoinduced electron transfer to promote diverse organic reactions. Herein, a heterogeneous transition metal-free material, a type of carbon nitride photocatalyst, potassium poly(heptazine imide), is employed to produce sulfonyl chlorides from arenediazonium salts under mild conditions (visible light irradiation, room temperature) with 50-95% yields. The method is suitable for the synthesis of both electron rich and electron deficient compounds, and it shows high tolerance toward different functional groups (halides, ester, nitro, cyano groups). Thus, a sustainable photocatalytic alternative to the Meerwein chlorosulfonylation reaction is offered.
Highlights
Synthesis of sulfonyl chlorides is one of the most important procedures and is part of the daily routine of an organic chemist
Sulfonamides, in turn, represent one of the biggest class of biologically active compounds used in pharmaceutical, agrochemical, materials, and food industries (Figure 1b).[1−3] Apart from this, sulfonyl chlorides serve as key intermediates in the synthesis of sulfonyl fluorides, sulfonate esters, sulfones, and sulfinic acids.[4]
A common method of sulfonyl chlorides synthesis is a Sandmeyer-type reaction proposed by Meerwein et al using copper salts, such as CuCl or CuCl2, as a catalyst for single electron transfer (SET) (Figure 1c).[8]
Summary
Synthesis of sulfonyl chlorides is one of the most important procedures and is part of the daily routine of an organic chemist. A common method of sulfonyl chlorides synthesis is a Sandmeyer-type reaction proposed by Meerwein et al using copper salts, such as CuCl or CuCl2, as a catalyst for single electron transfer (SET) (Figure 1c).[8] In the original work, arenediazonium salts, obtained from amines, reacted with SO2 in aqueous medium to yield the product in low-to-moderate yields. (several EUR per gram, if synthesis performed on the labscale) and high performance.[19,22,23] In addition, the heterogeneous nature of the catalyst allows for easy separation from the reaction mixture by filtration or centrifugation and its further reuse Such a combination of features of these materials is expected to improve the sustainability of organic synthesis. The reaction is mediated by heterogeneous potassium poly(heptazine imide) photocatalyst
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